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CD
BURNERS-SCSI
AUTHOR: Eduardo M. A. M. Mendes mendes@mgconecta.com.br
How to create multi-session cds using dir/=/dir.
TESTED ON: Unknown. Possibly COL (OLX) 2.3 Linux Kernel
2.2x
In order to use cdrecord it is first necessary to define to which scsi bus the cd-writer is connected. In my case the setup is dev=0,3,0. It is also interesting to have a separate directory in which all image files can be dumped: /home/cdsource is the directory I chose for dumping the images.
The best way of understanding how to create multi-session cds is to read README.multi. Most of what is going to be said here is based on that README file and on the help of several cdrecord users.
This Micro Howto is divided into two parts as follows:
a) Things that can be done
b) Things that can't be done (Of course, this is my point of view and perhaps you would have a solution to the problem I'll discuss later).
We are now ready to start.
a) Things that can be done
A simple example will demonstrate that we can create multi-session cds with the dir_feature of the type dir/=/dir1/dir2
Example
Objective: Saving root directories of Redhat 6.1 and Col 2.3 on a single CD.
Observation: Redhat installation is mounted on COL 2.3 at /mnt/redhat
First image - RedHat 6.1 - /mnt/redhat/root
mkisofs -D -l -r -f -m core -L -o image1.raw redhat/=/mnt/redhat/root
This will create a redhat directory on the cd. The option -D should be used with care. The other options used in the above command are just to demonstrate the use of mkisofs. Please refer to man mkisofs if you want to know more.
To see if the image is created as expected, we need to mount image1.raw using the option -o loop as follows:
mount -t iso9660 image1.raw /mnt/image -o loop
To see the contents type:
ls -l /mnt/image/redhat
Does it look ok? Great!
unmount /mnt/image
Now the burning process itself:
cdrecord -v -dev=0,3,0 -multi -eject image1.raw
To check the burned image we need to mount the cd; something like
mount -t iso9660 /dev/scd0 /mnt/cdroms
/mnt/cdroms is the mount point for scsi cdrom on my system.
Second image - Caldera 2.3 - /root
To create the second image on our cd, we need get information about sectors related to the first track. To do that, issue the command
cdrecord -v -dev=0,3,0 -msinfo
Cdrecord returns the following number
0,135563
This number is the format XX,YY discussed on README.multi. XX would be used for testing the images as well as burning the new track.
mkisofs -D -l -r -f -m core -L -C 0,135563 \ -M /dev/scd0 -o image2.raw empty_dir caldera/=/root
The above command creates an file called image2.raw which contains the root directory of my Openlinux installation. Please note that there is another entry, empty_dir, which is a workaround for a bug on mkisofs (Thanks, Jonas!). As the name says in an empty directory. If we don't do that we won't be able to see the first track, that is, the directory redhat.
Now we need to check of image2.raw is ok. The following command creates exactly what we need. Plese note that -C option. Only the first number changes in this case. The second one is always zero. In our case the first number is zero due to the cdrecord -msinfo. When more tracks are added to the cd this number will change.
mkisofs -D -l -r -f -m core -L -C 0,0 -M \ /dev/scd0 -o image2_test.raw empty_dir caldera/=/root
mount -t iso9660 image2_test.raw /mnt/image \ -o loop
ls -l /mnt/image shows that there are two directories: redhat and caldera just the way we wanted.
Now let us burn image2.raw (not image2_test.raw)
cdrecord -v -dev=0,3,0 -multi -eject image2.raw
We can mount the CD again and see that the two directories are there. We can carry on doing this until we decide to close the CD. If this is the case, don't use -multi when burning the last session.
b) Things that can't be done - dir1/dir2/=/dir3/dir4 and dir1/dir2a=/dir5/dir6
The above example seems a bit silly, one could argue. Why did I create a single directory called root and within two sub-directories: redhat and caldera?
Using the procedure described above we would do as follows:
mkisofs -D -l -r -f -m core -L \ -o image1.raw etc/redhat/=/mnt/redhat/etc
cdrecord -v -dev=0,3,0 -multi -eject image1.raw
To check the burned image we need to mount the cd; something like
mount -t iso9660 /dev/scd0 /mnt/cdroms
cdrecord -v -dev0,3,0 -msinfo
Cdrecord returns the following number
0,14391
The second image can be created using
mkisofs -l -r -f -m core -L -C 0,14391 \ -M /dev/scd0 -o image2.raw \ empty=/home/cdsource/empty_dir etc/caldera/=/etc
Creating a test image2
mkisofs -l -r -f -m core -L -C 0,0 \ -M /dev/scd0 -o image2_test.raw \ empty=/home/cdsource/empty_dir etc/caldera/=/etc
mount -t iso9660 image2_test.raw /mnt/image1 -o loop
Here is the problem: we only can see /etc/caldera. /etc/redhat is lost.
It would be a waste of time if you try to burn the second image (image2.raw).
I tried to as many options as possible but to no avail. Perhaps mkisofs has a bug!!!